Upon completion of their manufacture and prior to shipment, IC devices in the form of plastic encapsulated integrated circuits typically are subjected to an electrical property test in which the input-output characteristics, pulse characteristics, noise leeway, and the like of the individual IC devices are inspected. Those devices that pass the electrical property tests are then subjected to a so-called burn-in test. In this test the IC devices are placed in an oven and operated for a time at an elevated temperature, e.g., 140 degrees C., and under a voltage source that is greater than the rated value; those IC devices that continue to perform satisfactorily are then approved for shipment.
Sockets used for burn-in tests generally comprise a base for mounting a plurality of contact members for making electrical engagement with each of the electrically functional solder ball terminals of an IC device to be tested. As shown in U.S. Pat. No. 6,402,537, for example, an IC device to be tested is placed on a slider having an IC device receiving surface formed with an array of apertures that are arranged in the same pattern as the ball terminal grid array of the IC device. The slider is mounted on the base for reciprocal horizontal motion. The contact members each have two generally parallel contact beams extending into a respective aperture. A cam member is mounted on the base and is vertically movable downwardly in the z-direction toward the base against the bias of a return spring and cams the slider in an x-direction against the force of a slider return spring. A rib of the slider is disposed between each contact pair of contact beams and pushes one of the contact beams away from the other contact beam as the slider moves due to a downward force exerted by the cam when it is depressed to place the contact members in an open position to receive a corresponding ball terminal of an IC device to be loaded in the socket.
When the downward vertical force is removed from the cam member, the cam member and slider return to their original positions and with the contact beams of the contact members closing to make electrical engagement with respective terminal balls.
In order to use the same slider for IC sockets having different package sizes, it is known to use an adaptor that is custom made for a selected size that is in turn received on the slider. More recently sliders have come into use having integrated adaptor features that provide an IC device receiving seating surface with features for fine alignment as well as features for preventing or breaking free contact beams that may tend to stick to the terminal balls in preparation for removal of the IC devices from the socket at the conclusion of the testing procedure. An example of this type of integrated slider is shown in FIG. 3. In this type of slider having a grid array of apertures formed by intersecting x and y direction ribs, a plurality of wall extension portions extend upwardly along x-direction ribs from the top surface of the integrated slider. These wall extension portions have a common width with the ribs and provide a mesa like IC seating surface on each top end surface of the extension wall portions for receipt thereon of an IC device to be seated. The wall extension portions of a first set include several that are spaced apart in the y-direction a distance generally equal to the y-direction width of an aperture and are adapted to be received between x-direction rows of terminals of an IC device placed thereon to provide fine alignment.
A second set of two similar wall extension portions extend in the y-direction and have a width essentially the same as that of the ribs defining the apertures in that direction. The two wall extension portions of the second set are aligned with one another in the y-direction and are located contiguous to the first column (y-direction) of apertures corresponding to the main grid being employed in the IC device to be tested at one end of the main grid layout for the solder ball terminals of an IC device to be tested.
Extending from each of the second set of extension wall portions is an anti-stick feature in the form of a finger extending in the x-direction along respective x-direction ribs defining one side of the aperture of the first column and extending over that aperture. The fingers are each formed with a concave surface adapted to engage the center of a respective solder ball upon movement of the integral slider in the opening direction to thereby push the solder ball away from a respective contact beam providing an anti-stick function.
In this arrangement the first and second beams of each contact member extend through two adjacent apertures in an x-direction row with the rib separating the two apertures serving as a contact engagement and actuating member. The first and second beams extend in the z-direction above the top surface of the integrated slider defining the apertures but slightly below the IC device mesa like seating surfaces of the alignment wall extension portions.
The integrated slider discussed above accommodates different size packages while providing fine alignment of the IC device ball grid array relative to the contacts as well as an anti-stick function. However, as variations in the placement of dummy or outrigger balls for providing mechanical support for the IC device proliferate there are certain variations that cannot be accommodated in the prior art integrated slider, particularly due to the anti-stick structure that interferes with any aperture location immediately adjacent to the anti-stick features in the first y-direction column of apertures outside the area defined by the main grid of apertures for the electrically functioning solder ball terminals.